Sports shoe and a ground plate device

ABSTRACT

A sports shoe is disclosed for playing golf, having a sole fitted with a rotation mechanism, the rotation mechanism being provided with a rotary element rotatable against a biasing force provided to the rotary element by a biasing mechanism coupled to the rotary element. Further, a ground plate device is provided, in particular for use in playing golf, the ground plate device comprising a rotation mechanism, the rotation mechanism being configured to receive a section of a sole of a sports shoe, especially a golf shoe, and being provided with a rotary element rotatable against a biasing force provided to the rotary element by a biasing mechanism coupled to the rotary element. In a preferred embodiment, the ground plate device further comprises fastening means for detachably or not-detachably fastening the sports shoe.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. patent application Ser.No. 12/685,739, filed Jan. 12, 2010, which derives priority from U.S.Provisional Patent Application No. 61/146,729 filed Jan. 23, 2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a sports shoe and a groundplate device, in particular for playing golf.

2. Description of the Background

A ‘twisted knee’ is a common injury in number of sports such as golf,baseball, and field athletics as well as some physically demanding jobs.There is a need for a device which can act as a knee saver, a safety aidand as potentially as a therapeutic aid, once damage has been done, byallowing gradual increases in resistance, range and confidence to auser.

Of course the main use of aspects of the present invention will be inrelation to sports where any torsion of the body i.e. scything action isapplicable as with baseball, skiing, cricket, tennis or field hockey. Atorn meniscus is the usual medical indication of damage that cannot onlybe painful but may require long term treatment and may be careerlimiting for a professional athlete.

Ideally, the device should be able to provide aspects of the following:

-   -   Adjustable torque;    -   Torque profiling i.e. torque varies according to angle        bi-direction function;    -   Force/speed sensors with some kind of feedback;    -   Transmission to a smartphone;    -   Non-sports applications;    -   Game play e.g. skiing games (without the skis);    -   Orthopaedic anti-twist, post-knee and post-hip operations;    -   Alarm—if the torque is exceeded it sounds a whistle in ‘training        mode’;

Golf swing ‘follow-through’ leads to strain on knee ligaments becauseleft foot (right hander) cannot rotate on the ground due to studs. Someplayer's particular golf style leads to over-rotation and knee ligamentoverstrain. This has led to bone avulsions and joint disruption. Suchplayers may be an extreme (or just in the public eye) but the problem issurprisingly common. The problem resides in the rotation about a fixedfoot where the knee is the weak point—like an unfolding rope twist.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide animproved sports shoe and a ground plate device, in particular for use inplaying golf, avoiding the above-mentioned problem.

According to an aspect of the invention, a sports shoe, in particularfor playing golf, is provided, comprising a sole fitted with a rotationmechanism, the rotation mechanism being provided with a rotary elementrotatable against a biasing force provided to the rotary element by abiasing mechanism coupled to the rotary element.

According to another aspect of the invention, a ground plate device isprovided, in particular for use in playing golf, the ground plate devicecomprising a rotation mechanism, the rotation mechanism being configuredto receive a section of a sole of a sports shoe, especially a golf shoe,and being provided with a rotary element rotatable against a biasingforce provided to the rotary element by a biasing mechanism coupled tothe rotary element. In a preferred embodiment, the ground plate devicefurther comprises fastening means for detachably or not-detachablyfastening the sports shoe.

The invention enables the ball of the foot to rotate against a biasingforce provided e.g. by a spring, but only when the knee strain isexcessive. At all other times the shoe feels ‘normal.’ In one aspect ofthe invention, by “free-floating” against the biasing force a section ofthe sole on a bearing or slippery surface, the rotary mechanism is usedto soften the process of over extension; offloading the sudden tensionon the knee ligaments. Either a biasing element, e.g. a spring, can beof a fixed tension or adjustable to account for different styles andbody weights. In a preferred embodiment, the biasing element issufficiently tight to make the shoe seem normal for walking and othernon-rotational functions. The biasing force provided to the rotaryelement will restore the sole after the swing is over.

Advantageous developments of the invention are disclosed in dependentsub-claims.

In a preferred embodiment of the invention, the biasing mechanismcomprises a spring element providing the biasing force to the rotaryelement.

In another preferred embodiment of the invention, the biasing mechanismis provided as an adjustable biasing mechanism configured to adjust thebiasing force.

In still another preferred embodiment of the invention, the biasingmechanism is configured to adjust the biasing force in dependence on arotation position of the rotary element.

In an embodiment of the invention, the biasing mechanism is configuredto increase the biasing force in dependence on a rotation position ofthe rotary element.

In a preferred embodiment of the invention, the rotary element isprovided with a rotatable disc, the disc being rotatable against thebiasing force.

In a further embodiment of the invention, the rotation mechanism isreceived in a recess of the sole.

In still a further embodiment of the invention, on an outer surface ofthe rotary element a plurality of studs is provided.

In still another preferred embodiment of the invention, the rotaryelement has its rotation axis in a section intended to receive the ballof a foot. In an alternative embodiment, the rotary axis is provided ina section located back from the section intended to receive the ball ofthe foot.

The ground plate device may be provided with one or more of theadvantageous features disclosed for the sports shoe above.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features, and advantages of the present invention willbecome more apparent from the following detailed description of thepreferred embodiments and certain modifications thereof when takentogether with the accompanying drawings in which:

FIG. 1 is a composite view showing a sports shoe from below with arotary element in a normal position (A) and a rotary position (B),respectively, a rotary axis of the rotary element being located in asection intended to receive the ball of a foot.

FIG. 2 is a side cross-section view of the sports shoe of FIG. 1.

FIG. 3 is a composite view showing a sports shoe from below with arotary element in a normal position (A) and a rotary position (B),respectively, wherein the rotary axis is located back from the sectionintended to receive the ball of a foot.

FIG. 4 is a composite view showing in plan cross-section the use of dashpot type arrangements (A & B) to provide variable resistance to rotationin the rotary element device;

FIG. 5 is a composite view showing in plan cross-section variablemounting positions for a resistance bias such as a spring or hydro gasstrut in a rotary element device;

FIG. 6 is a composite view showing in side cross-section the use ofoverlapping surfaces for variation in rotational friction braking as aresistance in a rotary element device;

FIG. 7 is a composite view showing in side cross-section (A) and in plancross-section (B) variations in stud or spike distributions in a rotaryelement device; and

FIG. 8 is a side cross-section of an arrangement for “parking”(immobilizing rotation) in a rotary element device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Following the invention will be described in further detail, by way ofexample, with reference to preferred embodiments.

FIG. 1 shows a sports shoe 1 from below with a rotary element 2 in anormal position (A) and a rotated position (B), respectively. The rotaryelement 2 which is part of a rotary mechanism (see FIG. 2 below) isprovided as a disc like element. In case of using the sports shoe 1 forplaying golf, FIG. 1(B) represents the sports shoe 1 at the end of aswing where a spring 3 providing a biasing force to the rotary element 2is extended.

FIG. 2 shows the sports shoe from FIG. 1 in a side cross-section view.The rotary element 2 is fitted to a support element 4 embedded in thesole of shoe 1 by a rotary bearing 5. On an outer surface 6, the rotaryelement 2 is provided with studs 7 (e.g. golf spikes).

FIG. 3 shows a sports shoe 1 from below with a rotary element 2 in anormal position (A) and a rotary position (B), respectively, wherein therotary axis (14 in FIG. 1) is located back from the shoe 1 sectionintended to receive the ball of a foot.

The rotary element 2 described above, in another embodiment, may beprovided in a ground plate device (not shown) which is not part of thesports shoe of a user. The golfer may step on to the ground platedevice, in his/her current shoes for the demanding (and potentiallydamaging) drive. An external ground plate device, in preferredembodiments, incorporates one or more features described for the sportsshoe above. To specify, this external device (not included in a sportsshoe) leads to additional advantages. First, such an external groundplate device may be provided as a separate article. It would be easierto allow the heel component in an external plate, as well as adjustablepivot points/fulcrum to optimize the process. The act of turning on theball of the foot during a strenuous activity such as during sports hasinherent dangers particularly if not properly warmed up or on unevenground. However it is also important that footwear is sure, reliable andhas a predictable response even if adjustable for level of skill,exertion or training.

As indicated above, ideally and as potentially provided by aspects ofthe present invention, a device in footwear 1 is provided which allowsadjustable torque, torque profiling i.e. torque varies according toangle and use of bi-direction force/speed sensors with some kind offeedback function. The core of aspects of the present invention relateto provision of a specific rotational resistance control so asymmetricor lop-sided bias typically through a spring 3, or alternatively usingdash pot flows (described below) with fluids and hydraulics, along withsuitable sensors also discussed below. The non-uniform resistanceprovided by the present invention offers a more natural correlation withthe straining and stressing of the user's joint or joints, that is tosay knee, ankle and hip. It will be understood in a golf swing as theplayer turns, both in the back swing and in the follow through, theirbody through the joints essentially winds-up, placing strain on thosejoints. A constant resistance does not act sympathetically andproportionately with the player's movement but simply adds resistance somaking the chances of injury less as the user must act against the sameand uniform resistance throughout the activity rather than providingproportionate resistance just when need normally for example at theextremities of a golfer's swing. With the present invention theresistance to turning of the studs increases particularly at or towardsthe ends of the follow through swing whilst in the ‘power’ phase in themiddle of the swing the resistance is lowest and may be negligible. Insuch circumstances a player may feel more confidence to give it theirall without fear of over-stretching joints which may be advantageousparticularly with less skilled and/or less supple or/and heavierplayers.

Returning to FIG. 1 the rotary element 2 generally moves in thedirection A so that a rotational forward direction shown by arrow 10moves angularly between position 10 a in FIG. 1(A) and position 10 b inFIG. 1(B). The rotary element 2 is a disc seated within a recess 11 andacts against a bias spring 3 but it should be appreciated that therotary element 2 in the embodiment shown may be oval so that rotation ofthe oval rotary element 2 in recess 11 as shown in FIG. 1 (A & B) andFIG. 2 also provides increasing resistance with rotation with increasingrange. The combination of the bias spring 3 and rotary element 2engagement to recess 11 determines the resistance to turning in use.

It should also be understood that the rotary element 2 to recess 11association is frictional and susceptible to wear. In such circumstancescontinuous and ideally consistent engagement is achieved by renderingone or both of the mountings 12, 13 adjustable, such that they may beadjusted toward or away from each other. This allows for a pre-bias tospring 3 which load accommodates for any wear in the rotary element 2 torecess 11 engagement. The adjustment may be through spaced screw threadreceptacles 17 for seating the mountings 12, 13 (shown in dotted linesin FIG. 1(A), or other suitable separator or pull/push ratchet tocontact engagement. Such adjustment will also allow the range ofrotation and/or the resistance to rotation variation to be changeddependent upon requirements.

A mechanical spring 3 such as the illustrated extension spring can beused, but it should also be understood that rotational resistance can beprovided by other means including loaded or free dash pot arrangementsand hydro-struts.

FIG. 4 provides illustrations of dash pot arrangements to provideresistance, “dash pot” being herein defines as a damper which resistsmotion via viscous friction. For example, FIG. 4(A) shows a closedannular chamber 20 filled with a fluid, and one or two movable bafflesor blade elements 21, 22 within the fluid inside chamber 20. Uponrotation of the rotary element 2 fluid flow around the edges and/orapertures 23, 24 in the baffles or blades 21, 22 is restricted. Therestriction will be dependent upon rotational speed, the configurationof the edges, the size of the apertures 23, 24 and differences in sizebetween apertures 23, 24 in different baffles and blades 21, 22 as wellas the compressibility of the fluid in the chamber 20. In an embodimentone baffle or blade 21 may be fixed in the chamber 20 which in turn isfixed to the shoe body 1 whilst the other baffle or blade 22 may befixed to or associated with the rotary element 2, thereby give adifferential squeezing action in use.

It will be understood that a central hub 25 may include a bias spring(e.g., a torsion spring 19) or other biasing means which will alsoprovide resistance to rotation and return the device to an originalcondition. In any event some stop may be provided by a detent 18 in thechamber engaging the rotation baffle or blade 22 to stop furtherrotation. The detent 18 and/or the blade 22 or a part of the blade maybe flexible to prevent an abrupt stop but rather flexing of the blade orstop and so increased resistance to a stop over a range of rotation.

In FIG. 4(B) a further alternative is provided in which a small spiralelement 30 is provided in a chamber 31 filled with fluid so thatrotation of the spiral element 30 forces fluid into an open end or anend with apertures at least such that the narrowing spiral constrictsthe fluid providing increased resistance with further rotation. Acompressive element 33 such an inflated balloon or foam element orrubber insert may be placed in the spiral to provide further control offluid flow into the spiral and so rotational resistance.

In the above circumstances it will be appreciated that aspects of thepresent invention are not limited to a mechanical spring but rotationalresistance variation can be provide by a number of approaches includinguse of flexible foam or rubber or plastics materials in tension as wellas in compression across the fixed chamber or mounting to the shoe andthe rotor with studs or spikes.

It will be noted that the mountings 12, 13 in FIG. 1 are respectively ator near the edge of the rotary element 2 and the aperture 11 withinwhich the rotary element 2 is positioned. In terms of adjustment it willbe understood that the mounting 12 could be moved to a new positionnearer to the center 14 of the rotary element 2 and/or the mounting 13moved to a new position away from the edge of the aperture 11 in thesole of the shoe 1. Such shifts in the relative positions of themountings will alter the response of the bias to rotation and so the useof the shoe 1 in terms of restraining undue twisting about the joints ofa user. To allow adjustment typically the mountings will be upon innersurfaces of the shoe 1 so the rotary element 2 will be removed to exposethe mountings 12, 13 and so the bias 3 typically in the form of amechanical spring released so that the mountings 12, 13 positionschanged prior to re-assembly.

A number of mounting 12, 13 positions may be pre-determined and so thecombinations of mountings 12, 13 may be specified for user weight,ability and objectives in accordance with experience and/or through lookup tables. If the mountings 12, 13 are associated with slide or screwthread adjustment mechanisms or similar then a visible marking(alpha-numeric) may be used in selecting desired combinations to matchuser weight, ability, height and conditions.

FIG. 5 provides illustrations of different position for the mountings12, 13.

In FIG. 5(A) the mounting 12 for the resistance bias or spring 3 asillustrated and described previously is substantially on the rim of therotary element 2 but alternatively could be moved to a number ofpredetermined indexed positions 40 normally within in a quadrant or areamarked by a broken line 41 of the rotary element 2. The mounting 13 forthe spring 3 also can be as described previously at the edge of therecess 11 for the rotary element 2 but could be moved to a number ofpredetermined indexed positions 44 typically in a quadrant or areamarked by a broken line 45. It will be understood by varying therelative positions of the mountings 12, 13 that the response of the biasor spring 3 will be altered over the different extension and contractionlengths and so the rotational resistance response of a device.

In FIG. 5(B) a mounting 112 to a capstan or drum 100 is provided at oneend of a bias such as an elastic tether or belt 111 with the other endof the belt 111 secured to a mounting 113 which may be positioned in anumber of locations as required. The drum 100 may be changed in terms ofdiameter so that the winding of the belt 111 varies over a rotationalrange with changes in resistance. The drum 100 may be circular orcylindrical or oval again to alter the rotational response and soresistance in use.

It is by controlling resistance variation over a range and predictablythat particular advantages with the present invention can be achieved.Normally, as indicated above at least one and desirably two or moreresistance elements or bias mechanisms are provided including the spring3 or other compression or tension bias element, alone or in combinationwith frictional interference between rotary element 2 and sidewalls ofrecess 11 to accommodate it and possibly a simple friction rotationbrake about a mounting upon which the rotary element 2 is presented,although such a simple rotation brake by its nature imparts constantresistance rather than proportionate to rotation and so has limitedapplication with regard to aspects of the invention other than providingan activation force level for operation. Nevertheless it will beunderstood that in particularly sporting activities it is not desirableto be even or flat footed in terms of weight so normally it is desirableto be on the balls of the feet so leaning forwards with more weight onthe ball of the foot. This weight shift might be used to engage the biasmechanism to increase or decrease resistance in due proportion. Forexample with a friction brake more weight might increase friction and soresistance to rotation or a dashpot type arrangement is provided thenthe fluid flow thorough the regulator apertures in the baffle or rotorblades may increase or decrease when compressed to varying extents bythe weight shift to ball area of the shoe 1.

In FIG. 2 the support 4 is generally flat and provides a stable base forthe bearing 5 and rotary element 2 in the shoe 1. It will be understoodthat the support 4 provides an anchor in the shoe 1 but need notnecessarily be flat to spread load but may be shaped to concentrate loadfor friction resistance purposes so for example if slightly wedge shapedtowards the front or rear or side of the principal direction of the shoethe thicker end may come into more forcible engagement with a frictionsurface of the rotor so increasing resistance proportionately. Thesupport may also be slightly convex or concave or otherwise contoured toadjust and manage weight shifts to best advantage in terms of frictionengagement. It will also be understood that the support 4 could be asdepicted in FIG. 6(A), comprising a core 60 with a concentric collar 61in frictional engagement with each other so that as more weight W isapplied to the core 60 it is forced down (indicated by direction 62)resulting in more frictional engagement with the collar 61 at contactsurfaces 63 and more resistance, or vice versa. In such circumstancesthere may be some natural adjustment of resistance and variation thereoffor user weight, gait and posture. It will also be understood that,rather than a flat upright concentric ring surface engagement, theassociation could be tapered or conical or curved to enhance or decreasefriction surface engagement. This arrangement is depicted in FIG. 6(B)with a conical core 70 and counter-conical collar 71 in forcedengagement in the direction 72 with friction surface to surface contact73.

It should also be noted in FIG. 2 that the outer surface 6 of the rotaryelement 2 is not flat but rather curved (preferably convex) and that thespikes or studs 7 are not of uniform length. In use the shoe 1 and theuser will naturally rock or tilt in the direction of arrowhead C. Thecurvature of the outer surface 6 facilitates this natural rockingmotion. The rocking motion may be personal and distinct to a particularuser or type of user. In such circumstances as indicated above therotary element 2 may be removable/replaceable so that a range of rotaryelements 2 of differing curvature may be provided. The various rotaryelements 2 may be indexed and labeled to allow selection based on auser's preponderance for rock, roll and tilt, the curvatures beingmeasured so that a particular rotary element 2 curvature can berecommended for the individual user and this recommendation may bedependent upon skill level and conditions e.g. soft ground or hardground.

Traditional shoes for some sporting activities such as golf shoes havehad readily removable spikes or studs so that spikes or studs can beinter-changed for example between those suitable for Winter and Summer.It is expected that such inter-changeability will also be advantageouswith regard to aspects of the present invention. However, again withregard to the desire to provide tailored rotation resistance and controlit will be understood that rather than use the same spike or stud typeacross the sole of the shoe and rotary element 2 in accordance withaspects of the present invention variations in spike or stud type couldbe provided. Thus, the spikes or studs 80 as illustrated in FIG. 7 atthe front 81 or sides 82 or rear 83 of the rotor could have a differentlength or thickness or elasticity or taper, or otherwise vary to affectrotation resistance. An individual user may again be tested and arecommended spike or stud distribution and pattern suggested to thatuser which may even be different for each foot so respective shoe. Inview of the potential number and variation in stud types anddistribution (shown in FIG. 7(B)) with crosses for studs and holes forgaps in the distribution) it would be expected that the suggesteddistribution and pattern may be assembled into the shoe 1 by aspecialized retailer or sports technician who will also have thenecessary test and evaluation equipment to provide the suggesteddistribution and pattern.

It will be understood that comfort is a particular factor with shoes.The rotary nature particularly with a vigorous or a hefty user may meanthat there is a slight wobble or twist upon about the rotor in normalwalking. In such circumstance it is envisaged that the device inaccordance with aspect of the present invention as shown in FIG. 8 maybe ‘parked’ or immobilized by forwards 91 and rearwards 92 stamping inwhich the inline shift knocks a rotor mounting 93 to a locked positionwith a latch 94 preventing rotation and/or forces the rotor plate 95itself into engagement with a lock latch 96 to stop rotation. The lock94, 96 will be released by a reverse forwards or rearwards stamping sofreeing the rotor 95 to rotate as required in accordance with aspects ofthe invention.

By the above means it will be understood that it is possible to provideadjustable torque, torque profiling with angle, bi-directionalresistance by combination of bias, rotor shaft braking and rotor in arecess shaping.

In addition, sensors may be added to the shoe 1 (or at least astandardized test shoe to allow for customized shoes for an individualto be provided). Force, load and/or speed sensors may be associated withthe rotor, the recess accommodating the rotor, the mounting for therotor, the bias means such as for rate of spring extension, to thesupport for load distribution in a swing action along with other partsof the shoe. These sensors will prove absolute values in terms of highsand lows and transients, and also rates and trends useful in determiningthe right resistance profile over a range for an individual use or type.The sensors may be linked to processing means which analyze the resultsand suggest alteration in terms of movement and the positioning of thebias, the shape of the rotor and distribution as well as type of spikesor studs used.

The sensor(s) will tend to be electro-mechanical so force measurementwill be derived from strain gauges, or piezo electric devices. Forexample, FIG. 5(A) illustrates a conventional quartz rotary torquesensor 23 may be mounted to the axial central hub 25 of the rotaryelement 2 to provide feedback (signal out). Motion sensing will bederived from a magnet and coil device or with piezo surfaces, piezotuning forks, lasers and fluid pressure sensing (of a confined liquid).However any suitable sensor could be used from the basic to more complexinstruments. The sensor(s) may be in wireless contact with a personaldigital or mobile device such as smartphone to provide results butalternatively for example a simple LED light and/or audible sound/alarmin the shoe could illuminate or be operative if the range/rate ofrotation has been exceed or was within desired range. The sensors canalso be used to monitor a program or progress with an individual user intraining or convalescing in terms of increasing range in a controlledmanner after an injury or surgery and could provide a clinician with arecord as to activity with remedial therapy.

The features disclosed in this specification, claims and/or the figuresmay be material for the realization of the invention in its variousembodiments, taken in isolation or in various combinations thereof.

It should now be apparent that the above-described method and apparatuseffectively dampens the rebound of a lacrosse ball received in a head 10pocket particularly in which the webbing is stung taught according tothe rules of the game. Having now fully set forth the preferredembodiment and certain modifications of the concept underlying thepresent invention, various other embodiments as well as certainvariations and modifications of the embodiments herein shown anddescribed will obviously occur to those skilled in the art upon becomingfamiliar with said underlying concept. It is to be understood,therefore, that the invention may be practiced otherwise than asspecifically set forth in the appended claims.

What is claimed is:
 1. A sports shoe, in particular for playing golf,comprising a sole fitted with a rotation mechanism, the rotationmechanism being provided with a rotary element rotatable against abiasing force provided to the rotary element by a variable biasingmechanism coupled to the rotary element.
 2. The sports shoe according toclaim 1, wherein the variable biasing mechanism comprises a springelement providing the biasing force to the rotary element.
 3. The sportsshoe according to claim 1, wherein the variable biasing mechanismcomprises two or more biasing mechanisms configured to adjust thebiasing force by association with the rotary element.
 4. The sports shoeaccording to claim 1, wherein the biasing force provided by the variablebiasing mechanism proportionately changes on rotation of the rotaryelement.
 5. The sports shoe according to claim 4, wherein the biasingforce provided by the variable biasing mechanism increases on rotationof the rotary element relative to the sole.
 6. The sports shoe accordingto claim 1, wherein the rotary element comprises a rotatable disc, thedisc being rotatable against the biasing force.
 7. The sports shoeaccording to claim 1, wherein the rotation mechanism is received in arecess of the sole.
 8. The sports shoe according to claim 1, wherein aplurality of studs is provided on an outer surface of the rotaryelement.
 9. The sports shoe according to claim 1, wherein the rotaryelement has a rotation axis positioned relative to a section of thesports shoe adapted to receive a ball of a wearer's foot.
 10. A groundplate device, in particular for use in playing golf, comprising arotation mechanism, the rotation mechanism being configured to receive asection of a sole of a sports shoe, especially a golf shoe, and beingprovided with a rotary element rotatable against a biasing forceprovided to the rotary element by a variable biasing mechanism coupledto the rotary element.
 11. The ground plate device according to claim10, further comprising fastening means for detachably or not-detachablyfastening the sports shoe.
 12. The ground plate device according toclaim 10, wherein the variable biasing mechanism comprises a springelement providing the biasing force to the rotary element.
 13. Theground plate device according to claim 10, wherein the variable biasingmechanism is provided as a combination of biasing mechanisms configuredto adjust the biasing force by association with the rotary element. 14.The ground plate device according to claim 10, wherein the biasing forceprovided by the variable biasing mechanism proportionately changes onrotational position of the rotary element relative to the shoe.
 15. Theground plate device according to claim 13, wherein the biasing forceprovided by the variable biasing mechanism proportionately increasesdependent upon rotation position of the rotary element relative to thesole.
 16. The ground plate device according to claim 10, wherein therotary element is provided with a rotatable disc, the disc beingrotatable against the biasing force.
 17. The ground plate deviceaccording to claim 10, wherein the rotary element has a rotation axispositioned proximate a ball of a user's foot.